The present invention relates to anti-microbial proteins isolated from sugar beet.
An anti-microbial protein includes a protein (alone or in combination with another material) which is toxic or growth inhibitory under any circumstances to any micro-organism, including bacteria, viruses and particularly fungi. Such anti-microbial proteins include those that exhibit anti-microbial activity upon contact with a micro-organism and those that are anti-microbial as a consequence of assimilation or respiration thereof.
According to the present invention there is provided anti-microbial proteins isolated from sugar beet, wherein the anti-microbial proteins exclude chitinases and glucanases.
It is preferred that the sugar beet has been infected with a fungus of the genus Cercospora, and more particularly preferred that the proteins have been isolated from the leaves of sugar beet infected with Cercospora beticola.
The invention also includes a pure protein selected from those depicted in SEQ ID Nos 2, 5 and 8, or a functionally equivalent analogue thereof in which one or more amino acids have been added, substituted or removed without substantially reducing the protein's anti-microbial activity; or mixtures of such proteins or analogues.
The invention also includes a pure protein consisting of residues 80-111 in SEQ ID No. 8, or residues 29-74 in either SEQ ID No. 2 or SEQ ID No. 5, or a functionally equivalent analogue thereof in which one or more amino acids have been added, substituted or removed without substantially reducing the protein's anti-microbial activity; or mixtures of such proteins or analogues. Proteins having the amino acid sequences of residues 29-74 in SEQ ID Nos 2 and 5 are hereinafter referred to as AX1 and AX2 respectively, and protein having the amino acid sequence of residues 80-111 in SEQ ID No. 8 is hereinafter referred to as AX3.1
Infection of plants with fungal or viral pathogens may induce a synthesis of about 10 families of homologous pathogenesis-related proteins (PR proteins) in vegetative tissues. Such PR-proteins have been classified into 5 groups. The PR-2, PR-3 and PR-5 proteins are beta-1,3-glucanase, chitinases and thaumatin-like proteins respectively. Specific functions have not been assigned to the PR-1 and PR-4 groups of proteins. The PR-4 proteins are similar to C-terminal domains of prohevein and the putative wound-induced WIN proteins of potato, thus lacking the N-terminal hevein domain. "Basic counter-part of the acidic pathogenesis-related 4 group of proteins" thus includes the basic counter pan of proteins similar to the C-terminal domains of prohevein and the putative wound-induced WIN proteins of potato.